Method and apparatus for shaping glass sheets

ABSTRACT

GLASS SHEETS ARE SHAPED BETWEEN PRESS SHAPING MOLDS HAVING FORAMINOUS SHAPING SURFACES. HEATED GAS AND COOLED GAS ARE APPLIED THROUGH THE FORAMINA OF THE SHAPING SURFACES TO SEPARATE THE SHEET FROM A FORAMINOUS SURFACE IN CONTACT WHEREWITH AND TO COOL THE GLASS SHEET RESPECTIVITY. RECIPROCATING MEMBERS ENGAGE THE EDGES OF THE SHEET TO RECIPROCATE THE SHEET IN A GENERALLY HORIZONTAL DIRECTION UNTIL THE GLASS SHEET IS NO LONGER IN A DEFORMABLE STATE.

6 Sheets-Sheet l ATTORNEYS R. G. FRANK METHOD AND APPARATUS FOR SHAPINGGLASS SHEETS March 30, 1971 Filed March 11, 1968 I, I m b a 4 L om m M im M H d m W k g ,N v a v w J-" R M 8 4..." w n 0 0 o o v m ms wk 0% R 1.5 m mm Q lo. mm L u ||l|IlI|||Jvlrl .llln \llllllllllllllh II "I -m r 25 an.

March 30, 1971 FRANK 3,513,022

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METHOD AND APPARATUS FOR SHAPING GLASS SHEETS Filed March 11, 1968 6Sheets-Sheet s I I III LIL: 11.. 1 I

INVENTOR ml 2 55107 6. PIP/4m BY QA ORNEYS R. G. FRANK March 30, 1971METHOD AND APPARATUS FOR SHAPING GLASS SHEETS Filed March 11, 1968 6Sheets-Sheet 4 INVENTOR 208E127 @FRA -08, ATTORNEYS 30, 1971 R. G. FRANK3,573,022

METHOD AND APPARATUS FOR SHAPING GLASS SHEETS Filed March 11, 1968 6Sheets-Sheet 5 INVENTOR mas/a7" a. FKAI b BY M 4 ORNEYS March 30, 1971METHOD AND APPARATUS FOR SHAPING GLASS SHEETS Filed March ll, 1968 R. G.FRANK 6 Sheets-Sheet 6 HEMATIC ELECTRICAL CONTROLS "U ACT'VATES 1co-vEYo2 CLUTCH TIMER} CLOSES 5W 10555 i 2% c ,gzl sy fi ACTUATES 'r-z-JfiIEAq PISTON 49 ACTUATES HEZ] fi fiifi FE EE lE' PISTON 49 AcrumzsCLOSES L LE4 OPENS sv-a STARTS L i L- J PISTON 72 v ACT ATES MULTIVIBIZATOR. MV I W \EHE E JE PISTON 82 LOSES @um LS-Z A A-I M01021"JEEP-Vii) SHUTTLE cm! 90 LS-3 ED555115- FINGERS I02 ACTU ATES REVEBSESMOTOR- ur sugrgLs CA 0 T e OPENS 5V4 0P5N5 INVENTOR SV-Z 055.41 0.FRANK. FIG. 10

A ORNEYS United States Patent 3,573,022 METHOD AND APPARATUS FOR SHAPINGGLASS SHEETS Robert G. Frank, Tarentum, Pa., assignor to PPG Industries,Inc., Pittsburgh, Pa. Filed Mar. 11, 1968, Ser. No. 711,946 Int. Cl.C03b 23/02 US. Cl. 65104 17 Claims ABSTRACT OF THE DISCLOSURE Glasssheets are shaped between press shaping molds having foraminous shapingsurfaces. Heated gas and cooled gas are applied through the foramina ofthe shaping surfaces to separate the sheet from a foraminous surface incontact therewith and to cool the glass sheet respectivity.Reciprocating members engage the edges of the sheet to reciprocate thesheet in a generally horizontal direction until the glass sheet is nolonger in a deformable state.

The present invention relates to bending glass sheets, and particularlyrelates to an improvement in shaping glass sheets by a press bendingoperation.

In a typical press bending operation, a series of glass sheets areconveyed through a furnace at a rate of speed that is correlated withthe amount of heat supplied in the furnace to raise the temperature ofeach sheet of glass to its deformation temperature. When the leadingsheet of glass in this series attains the desired temperature, it leavesthe furnace and enters a shaping station. There, the heat-softened glassis press bent to a desired curvature between complemental shapingsurfaces formed on the inner faces of a pair of contoured shaping molds.The glass sheets are then chilled as rapidly as possible if it isdesired to temper the bent sheets after they are shaped.

In recent years, curved glass sheets have found increasing use as faceplates for television tubes and as windows for automotive vehicles. Thedemand for these products has necessitated the development of massproduction techniques to produce large quantities of curved glass sheetswith a minimum of manual labor. The present invention provides acommercially practical mass production operation for producing curvedglass sheets having very close dimensional tolerances throughout theirentire extent, acceptable optical properties and uniform curvature fromsheet to sheet.

Apparatus used to perform the above method usually comprises a pair ofcontoured shaping molds having foraminous shaping surfaces conforming tothe shape desired for the opposite major surfaces of the bent glasssheet. According to the present invention, as least one of the moldscomprises a chamber having a foraminous contoured wall conforming to theshape desired for a major surface of the glass sheet after bending. Inorder to avoid establishing a pattern of iridescence in the glassresulting from its non-uniform chilling immediately after its shaping,the present invention suggests reciprocating the glass sheet relative tothe mold foramina during its quenching immediately following the pressbending operation.

Apparatus for performing the present invention comprises a framebridging a shaping mold and having glass edge engaging fingers extendingthrough notches in the mold to beyond the mold. The fingers are spacedfrom one another a distance slightly greater than the correspondingdimension of the glass sheet.

Means is provided for reciprocating the frame and its glass engagingfingers at a frequency and displacement that is correlated with thearrangement of the apertures in the shaping mold so that the glassmovement is sufficient in both amplitude and frequency to avoidestablishing the iridescent patterns resulting from chilling the glassthrough spaced apertures without providing relative movement. Controlmeans is also provided to control the program of reciprocating the frameand the glass engaging fingers with the application of cold fluidagainst the major surfaces of the press bent glass sheet so that bothoperations take place simultaneously.

According to a particular embodiment of the present invention, the moldopposite the first mold comprises a second chamber having a foraminouscontoured wall conforming to the shape desired for the opposite majorsurface of the glass sheet after bending. Both mold chambers haveoperatively connected thereto fluid supply means for introducingrelatively cold fluid to each chamber for exhaust through its foraminouswall. The program control means operates for both molds so that theintroduction of cold fluid takes place in unison into the two chambersas well as simultaneously with the reciprocation of the glass engagingfingers.

One of the molds has an outer wall of concave configuration. The othermold has an outer wall contoured to a convex configuration. It isusually desirable to apply fluid through only one of said wallsimmediately after bending the glass sheet to help disengage the sheetfrom the molds before applying the quenching fluid against both surfacesof the bent glass sheet. The present invention optionally includes meansto control the selective application of fluid to one side only of thebent glass to help disengage it from the mold.

Means for providing relative movement of the foraminous contoured wallsbetween a closed position and a retracted position is provided in anillustrative embodiment of the present invention. In addition, whendesired, means responsive to the relative movement of the contouredwalls toward a retracted position initiates the introduction of thefluid through the mold having a convex outer wall to help separate thebent glass from the convex wall. Immediately thereafter, relatively coldfluid is rapidly introduced into both mold chambers to chill both bentglass surfaces.

Relative movement between a glass sheet and opposing molds having glassquenching apertures in planes parallel to the major glass surfaceslessens iridescent patterns resulting from non-uniform cooling of theglass sheet. The prior art moved the molds to perform such relativemovement. Since molds are usually very heavy, powerful motors andaccessory motive equipment are used to reciprocate the apertured molds.Furthermore, motive equipment reciprocating the molds at a rapid enoughfrequency to avoid an iridescent pattern establishes vibration that isvery uncomfortable for personnel tending the equipment.

The reciprocatory motion imparting equipment required for such heavyequipment requires a large initial capital investment. Such massiveequipment is likely to break down frequently. Much production time islost repairing the expensive equipment. In addition, an inventory ofrelatively expensive parts must be kept.

The present invention suggests moving the glass sheet rather than themolds in a two-and-fro motion after press bending. The motion impartingequipment needed to move the light, bent glass sheet relative to themold apertures is very light, thus enabling it to respond rapidly toactuation and deactivation and to reciprocate at a suflicient frequencyand amplitude to avoid establishing the iridescent pattern.

According to an illustrative embodiment, the motion imparting meanscomprises glass edge engaging fingers that contact alternate oppositeglass edges to displace the glass sheet across the space between theretracted molds. Since the glass floats, it is free to move in anarcuate plane in substantially fixed spatial relation between the molds.Mold moving apparatus is not capable of maintaining a fixed spacebetween the glass and the molds.

A particular embodiment of the present invention will now be describedin order to provide an illustrative example of the present invention. Inthe drawings which form part of the description, and where likereference numbers are applied to like structural elements:

FIG. 1 is a fragmentary longitudinal side elevation of a press bendingapparatu incorporating the novel features of the present invention;

FIG. 2 is a schematic view transverse to that of FIG. 1 of selectedportions of the press bending apparatus of the present invention;

FIG. 3 is a fragmentary plan view of a portion of the apparatus shown inFIGS. 1 and 2 with parts omitted to show other parts more clearly;

FIGS. 4 through 8 are schematic views showing the relative positions ofvarious moving elements forming part of an illustrative embodiment ofthe present invention taken at different stages of a press bendingoperation;

FIG. 9 is a fragmentary, perspective view of a portion of the lowershaping mold used for press bending glass sheets with certain partsremoved to show other parts in detail; and

FIG. 10 is a schematic electrical circuit diagram explaining thesequential operation of the above illustrative embodiment of theinvention.

Referring to the drawings, a typical apparatus illustrating the presentinvention comprises a conveyor system 11 which extends horizontallythrough a furnace 12, a shaping and quenching station 14, and additionalcooling apparatus 16. The three elements traversed by the conveyorsystem are disposed in end to end relationship between a loading station(not shown) at the front end of the conveyor system 11 and an unloadingstation (also not shown) at the other end of the conveyor system.

The furnace 12 is of tunnel-type configuration and has heating elements17 disposed in rows and columns to radiate heat downward and upwardtoward a first conveyor section 18 of the conveyor system 11. The firstconveyor section 18 comprises a plurality of longitudinally spacedhorizontally extending continuous conveyor rolls 19 disposed forrotation about transverse axes through out the loading station and thelength of the furnace 12. A motor M1 drives the rolls 19 in unison at auniform rate of rotation which is preselected to coordinate with theamount of heat provided by the heaters 17 in the furnace 12 so as toirradiate glass sheets conveyed through the furnace to heat the sheetsto a temperature such that when the leading sheet leave the furnace itis at a deformation temperature desired for its subsequent operation.

The conveyor system continues with a second conveyor section 20' whichextends through the shaping and quenching station 14. The secondconveyor section 20 incorporates additional continuous rolls 19 fore andaft a plurality of stub rolls 21. A motor M-2 operates the secondconveyor section 20 at a relatively high speed intermittently in amanner to be described in greater detail subsequently. An overrunningclutch arrangement (not shown) selectively couples the last six rolls ofthe first conveyor section 18 to the motor M2. This enables the last sixrolls to rotate normally at the speed of the first conveyor section 18except when the second conveyor section 20 is actuated. In the lattercase, the last six rolls of the first conveyor section 18 rotate at thefaster intermittent speed of the second conveyor section 20.

The conveyor system 11 concludes with a third conveyor section 22 whichextends through the additional cooling apparatus 16 and the unloadingstation which is not shown. The third conveyor section 22 comprises amotor M-3 driving a series of continuous, horizontally spaced,transversely extending rolls 23 to rotate the latter 4- so that theypropel a series of bent glass sheets to an unloading station (notshown).

The entire conveyor system 11 is supported on a framelike conveyorsupport structure 24 which includes bearing support beams 25 extendinghorizontally in spaced parallel pairs on the outer lateral sides offurnace 12 and the shaping and quenching station 14 and the additionalcooling apparatus 16. The bearing support beams 25 in turn are supportedon spaced vertical legs 26.

A glass sensing device, comprising a source of light 27 disposed on oneside of the conveyor and a photosensitive device 28 adapted to produce asignal in response to light of a certain intensity disposed on the otherside of the conveyor, is located before the exit of the furnace 12 inposition to detect the presence or absence of a glass sheet G. The glasssensing device is constructed to impart an electrical signal when theleading edge of a glass sheet G passes between light source 27 andphotosensitive device 28.

The furnace 12 may either be of the electric resistance type or of thegas burner type or one using a combination of gas and electric heaters.Provision is made for adjusting the intensity of heat radiated from eachof the individual heaters 17 disposed in facing relation to the path oftravel of glass sheets along the first conveyor section 18 so as to havethe sheet arrive at the shaping and quenching station 14 at the desireddeformation temperature.

All the rolls in the conveyor system are one inch diameter stainlesssteel shafts extending horizontally transversely of the conveyor systemand are spaced longitudinally along the conveyor path. All the rollsexcept the stub rolls 21 are mounted on three inch centers. The stubrolls are spaced six inches lengthwise of the conveyor from one anotherand from the adjacent continuous rolls. In order to prevent the glasssheets from being subject to loss by chill cracking, the conveyor rollsoutside the furnace 12 are covered with stretched, braided fiber glasssleeves having a nominal diameter of inch and stretchable to fit snuglyover the conveyor roll which it covers.

A preferable mode of operation of the furnace i to have the upperheaters 17 radiate heat downward more intensely onto the upper majorsurface of the glass sheets G conveyed along the first conveyor section18 than the lower heaters radiate heat upward onto the lower majorsurface of the moving glass sheets. Such a disposition tends to warp thesheets into a slightly domed configuration so that the glass sheets makecontact with the conveyor rolls only along their longitudinal side edgeas depicted in U.S. Pat. No. 3,245,772 to James H. Cypher and Charles R.Davidson. This technique keeps the rolls from marking the viewingportions of the glass sheets that are treated. The upper and lowerheating elements 17 in the furnace are energized to provide a heatingpattern having a temperature gradient decreasing from the longitudinalcenter to each side thereof as well as a top to bottom difference todiiferentially heat the glass sheets passing through the furnace.

The shaping and quenching apparatus at the shaping and quenching station14 is supported on a support frame generally depicted by referencenumber 30. The support frame comprises an upper horizontal frame 32 anda lower horizontal frame 34. A plurality of vertical members 36interconnect the upper and lower frames to form a unitary structure. Alower piston housing 38 having an upwardly extendable piston 39 has itsfree end attached to a platform connected to the lower end of a lowermold 40.

The mold 40 comprises an upper foraminous contoured wall 41 forming theroof of a chamber 42. Clearance notches 43 are provided along oppositesides of the chamber 42 for purposes to be explained later. Theforaminous wall 41 is contoured to provide an upward facing shapingsurface conforming to the shape to be imparted to the lower majorsurface of the glass sheet.

Wall 41 is preferably convex so that the bent glass is shaped to haveits viewing area out of contact with any conveyor rolls.

In order to keep the lower mold 40' in proper alignment and moving in avertical axis of movement, a plurality of vertical sleeves 44interconnected by reinforcements 45 are provided to receive guide rods46 extending downward from the rear of the platform supporting the lowermold 40.

The lower piston 39 is constructed and arranged with respect to thelower mold 40 in such a manner that in its retracted position, the upperforaminous contoured wall 41 of the lower mold 40 lies entirely belowthe horizontal plane tangential to the upper extremity of stub rolls 21.This provides clearance for a glass sheet G to enter or leave theshaping station 14.

The notches 43 are aligned with the stub rolls 21. Their size permitsthe lower mold 40 to be moved upward into a position wherein its curvedshaping surface formed at the upper surface of the foraminous contouredwall 41 lies above the horizontal support plane provided by stub rolls21. The lower piston 39, when extended, lifts the shaping surface of thelower mold above the stub roll support plane.

A lug 47 is carried by the lower mold 40. A pair of limit switches LS-land LS-2 are supported in position for actuation by the lug 47 duringcertain movements of the lower mold 40' during a press bending operationas will be explained in greater detail later The pressing station 14also comprises an upper piston housing 48 carried by the upperhorizontal frame 32. An upper piston 49 is movable within the upperpiston housing 48 and is attached at its lower end to an upper mold 50.The latter comprises a lower foraminous contoured wall 51 whose lowersurface conforms to the shape desired for the upper surface of the glasssheet to be shaped. The upper mold 50 also comprises a hollow chamber52, similar to chamber 42 for the lower mold 40. In addition, the uppermold may also have clearance notches 53, if desired. The notches 53 arealigned with the notches 43 of the lower mold 40, if present.

It is important that the upper mold 5t] move in a vertical directionalong an axis parallel to the axis of movement of the lower mold 40.Consequently, brackets 54 depending from the upper horizontal frame 32are provided with apertured ears 55 which serve as sleeves to guide themovement of guide rods 56. The latter are attached to the rear of theupper molds 50.

In order to provide hot gas at certain phases of the operation and coldair at other phases of the operation, a hot gas supply pipe 57 isconnected to the chamber 52 for the upper mold 50 and an additional hotgas Supply pipe 58 is connected to supply hot gas into chamber 42 of thelower mold 40. An oven 59 serves as a source for hot gas which isdelivered as desired through a solenoid valve SV-1 and the hot gassupply pipe 58 to the lower mold chamber 42 and through another solenoidvalve SV2 and hot gas supply pipe 57 to the upper mold chamber 52. Bothhot gas supply pipes are flexible, and may supply the chambers fromfurnace 12.

A compressor or other source of cold air 60 is connected through stillanother solenoid valve SV3 to flexible cold air supply pipes 61 and 62.The cold air supply pipes 61 supply cold air under pressure to the lowermold chamber 42 and flexible cold air supply pipes 62 supply cold airunder pressure to the upper mold chamber 52 whenever solenoid valve SV-3is open.

A spring 63 is entrained about each of the guide rods 56 and extendsbetween a bracket 64 at its lower end and an apertured frame 65 at itsupper end. When the upper mold 50 is retracted sufficiently to have theapertured frame 65 came into contact with the apertured ears 55, thesprings 63 provide resilient resistance to further upward movement ofthe upper mold 50. Cross braces 66 extending generally horizontally in ahorizontal plane below that occupied by the upper horizontal frame 32 ofthe support frame 30 interconnect the brackets 54 and also provideadditional support for the lower end of the upper piston housing 48. Theupper mold 50 is attached to the lower end of the upper piston 49 tocause the upper mold 50 to move downward in response to extension of theupper piston 49 in a downward direction and upward in response toretraction of the upper piston 49.

The foraminous contoured walls 41 and 51 are made of a refractorymaterial, preferably one having a coefficient of heat conductivitybetween 3 and 5 British thermal units per hour per square foot of areaper degree Fahrenheit difference per inch of thickness. A refractorymaterial having about 99 percent by weight in a heat resistant bindersold by the trade name of Glass Rock and another sold under the tradename of "Masrock are suitable materials. Another suitable material is anasbestos cement board sold under the trade name of Transite.

The wall material is ground to the desired curvature and drilled toproduce apertured pressing faces. The apertures 67 of the illustrativeembodiment are A; inch diameter holes arranged in oblique rows spacedapart /2 inch from each adjacent aperture. The apertures through thecontoured walls 41 and 51 extend substantially normal to the walls.Additional apertures 68 (FIG. 9) extend diagonally through the wallsformed by the notches 43 and 53 to insure that the entire glass sheet isexposed to successive baths of fluid that are as uniform as possible forthe glass sheet before quenching and provide a uniform rate of chillingduring quenching.

The chambers 42 and 52 are of metal and are secured to the marginalportion of the refractory walls 41 and 51 in any suitable manner. FIG. 9illustrates one example of attachment by recessed screws.

The upper mold 50 also supports a glass reciprocating mechanism attachedby lugs 70 for movement with piston 49. The glass reciprocatingmechanism comprises a cylinder housing 71 supporting a piston 72 forextension in one direction horizontally and another housing 81 (FIG. 3)supporting a piston 82 for extension in the opposite horizontaldirection. Attached to the free end of the piston '72 is a verticalfinger 74. The latter is attached at its lower end to a horizontal bar76. A similar finger 84 and horizontal bar 86 are similarly attached topiston 82. Pistons 72 and 82 are alternately extended to reciprocate thehorizontal bars 76 and 86. A pair of horizontal arms 77 and 87 areattached to the longitudinal extremities of the horizontal bars 76- and86 and extend at right angles to the horizontal bars. Vertical arms 78and 88 having glass engaging fingers 79 and 89 at their lowermost endsare attached and extend downward from the horizontal arms 77 and 87. Thearms 78 and 88 and fingers 79 and 89 are disposed in locations toreciprocate within the clearance notches 53 for the upper mold 50. Thefingers 79 and 89 are usually arranged in sets so that there is one pairof opposite fingers 79 and 89 for each notch 53, although two pairs ofspaced fingers suffice for many glass sizes. The fingers '79 and 89opposite one another are spaced apart about A inch more than thecorresponding dimension of the glass sheet G. Suitable control circuitrywill be described later to explain how the glass reciprocator apparatusworks in timed sequence to the other operations of the press bendingapparatus.

The apparatus of the illustrative embodiment also in corporates atransfer carriage or shuttle car 90 that transfers a bent glass sheetfrom the shaping and quenching station 14 to a position along the thirdconveyor section 22. However, the shuttle car is not necessary in caseswhere production requirements are such that the bent glass may besubjected to a longer period of quenching with chilling fluid at theshaping: station. In such cases, the bent glass sheet G is depositedonto the stub rolls 21 of the conveyor and the latter rotated to removethe bent glass from the shapingand quenching station .14 to theadditional cooling station 16.

The third conveyor section 22 extends through an additional coolingstation 16 where the bent glass is cooled to a lower temperature thanthat at which it leaves the shaping station 14. To accomplish this end,the additional cooling station 16 is provided with an upper plenumchamber 91 and a lower plenum chamber 92 disposed above and below theplane of support provided by the conveyor rolls 23. The plenum chambersare carried in an enclosed housing and have openings, preferably in theform of spaced, opposed slots extending transverse to the path of glasssheet movement along the upper tangential plane common to the conveyorrolls 23.

The shuttle car 90 is of open frame construction and comprises twoopposed longitudinally extending rod members 93 and 94, each supportinga pair of apertured bracket members 95 and 916, respectively. Thelatter, in turn, support depending wall members 97 and 98, respectively.Each wall member 97 and 98 supports a piston cylinder 99. Each of thelatter has a piston 100 provided with a glass engaging finger 102 at itsfreen end. All four fingers 102 are extended simultaneously throughnotches 43 when the lower mold 40 engages a glass sheet against theupper mold 50 during press bending. Thus, when the lower mold 40retracts, the glass sheet G is deposited on the extended fingers 102.

The longitudinally extending rod members 93 and 94 extend horizontallyfor a major portion of their length, then are curved upward andobliquely rearward toward one another until they meet at a bracket 104to which they are connected rigidly. The bracket is attached to a drivebelt 106 entrained upon a driving rod 107 and a driven rod 108. Thelatter rods are rotatably supported in brackets 109 and 110. A reversingmotor 111, mounted on bracket 109, actuates the drive belt 106 throughpulleys fixed to the rods 107 and 108. A limit switch LS-3 is positionedfor actuation by bracket 104 whenever the shuttle car 90 reaches itsrearmost position.

OPERATION Glass sheets G are mounted in series and conveyed through thefurnace 12 along the rollers 19 of the first conveyor section 18 at aspeed synchronized with the intensity of heat radiated by the furnaceheating elements 17 so that the glass sheet reaches the shaping andquenching station 14 at a temperature sufficient for rapid deformationand tempering.

The glass sensor 27, 28 detects the leading edge of a glass sheet Gshortly before the latter leaves the furnace 12. At this stage, theoutput circuit of the glass sensor 28 actuates a conveyor clutch timerthat engages the conveyor clutch for a predetermined time to rotate thelast six rolls of the first conveyor section 18 together with the rollsof the high speed second conveyor section and closes solenoid valves SV1and SV-2, thus shutting off the flow of hot fluid into chambers 42 and52.

FIG. 4 shows a glass sheet G arriving at the shaping station 14 with theshaping molds 40 and 50 retracted. The schematic views of FIGS. 4 to 8exaggerate the mold spacing. Actually, the maximum mold separation neednot exceed 1 inch for handling the usual variety of glass thicknessesusually processed (thicknesses up to a nominal inch thickness).

The molds are at a temperature [within a temperature range such that theheat transfer rate between the hot mold and the glass sheet isapproximately uniform throughout the entire extent of the glass sheet G.A preferable temperature range for the mold shaping surfaces is between600 and 750 degrees Fahrenheit. When the contoured, foraminous moldwalls are in this temperature range, the heat transfer rate of the glassportions facing the foramina of the contoured mold walls approximatesthat of the glass portions coming in direct contact with the shapingsurfaces of the contoured molds.

The glass sensor 28 also actuates a timer circuit T-l which extends thelower piston 39 upwardly and the 8 upper piston 49 downwardly for alimited time suificient to have the lower mold lift the glass sheet Gabove the stub rolls 21 and into engagement with the lower surface ofthe upper mold 50. The springs 63 provide a resilient backing for theupper mold in case a glass sheet of excessive thickness is treated. FIG.5 shows the glass sheet G sandwiched between the molds during itsshaping.

As the lower mold 40 rises, its lug 47 trips limit switch LS1 to actuatea timer T2. After a predetermined time delay suflicient for the molds toshape the glass sheet, the timer T2 causes the upper mold piston 49 toretract a short distance. In addition, timer T2 opens the solenoid valveSV1 to supply hot fluid to the lower mold chamber 42. The upward flow ofhot fluid through the foramina or apertures 67 and 68 of the contouredupper wall 41 of the lower shaping mold 40 with the upper mold 50retracted helps remove the bent glass sheet G from its embrace with thelower mold 40. Hot fluid is preferably supplied at a rate of between 300and 350 cubic feet per minute of the combustion products of natural gasper square foot of commercial plate, sheet or float glass ofsoda-lime-silica composition.

Timer T2 also activates a timer T3, which stops the retraction of theupper mold piston 49 after a predetermined time interval so that theupper and lower molds are separated by a desired distance. This distanceis preferably about 0.3 to 0x4 inch plus the glass thickness. (About .45inch separation is suitable for glass sheets of /8 inch nominalthickness and about .6 inch separation is suitable for glass sheets of 3inch nominal thickness.) At the same time that the upper mold movementstops, the glass is floating between the molds as shown in FIG. 6 andtimer T3 actuates a timer T4.

Timer T4 immediately closes solenoid valve SV-l to cut off the supply ofhot fluid to the lower mold chamber 42 and opens solenoid valve SV3 tosupply cold fluid under pressure to both mold chambers 42 and 52.Preferably the rate of cold air flow is between 2000 and 2500 cubic feetper minute per square foot for A; inch thick glass and between 1300 and1500 cubic feet per minute per square foot for 5 inch glass. Thesevalues are expressed for commercial plate, sheet or float glass ofsoda-lime-silica composition.

Also, timer T4 starts the operation of a multivibrator circuit MV thatis preferably set for cycles per min ute. The multivibrator alternatelyactuates the oppositely disposed pistons 72 and 82 to cause the glassengaging fingers 79 and 89 to reciprocate, thereby imparting linearreciprocating movement to the bent glass sheet while the latter floatson a cold air cushion formed from blasts through the foramina 67 and 68of the contoured, foraminous walls 41 and 51 of the respective shapingmolds 40 and 50. FIG. 7 shows this step. The curved sheets float in acurved path parallel to the mold contours with fingers 79 and 89engaging opposite edges alternately.

In addition, timer T4 actuates a timer T5 that extends the shuttle carfingers 102 by actuating the four pistons 100 simultaneously. After apreset time, timer T5 closes solenoid valve 'SV-3 to cut off the supplyof cold fluid to the mold chambers 42 and 52, thereby permitting thebent glass sheet to lower itself onto the extended fingers 102. At thesame time, timer T5 disconnects the multivibrator circuit MV todiscontinue operation of the glass reciprocator and completely retractsthe mold pistons 39 and 49.

The lower mold 40, on retraction with the lower mold piston 39, causeslug 47 to trip limit switch LS2. The latter, in turn, actuates motordrive 1.11 to transfer the shuttle car from a position where fingers 102are disposed in alignment above the mold notches 43 to a position beyondthe shaping station 14 where bracket 104 engages limit switch LS-3. Whenthe shuttle car moves to this latter position, its extended fingers 102support the bent glass sheet G for displacement from the bending andquenching station 14 to the additional cooling station 16. FIG. 8 showshow the fingers 102 support the bent glass G for removal from station14.

When limit switch LS3 is engaged, it deactivates the pistons 100,thereby permitting them to retract the fingers 102. This action depositsthe bent glass sheets onto the conveyor rolls 23 of the third conveyorsection 22. At the same time, limit switch LS-3 actuates a timer T-6that energizes the motor drive 111 in reverse until the shuttle car 90is in position at the shaping and quenching station 14 with its fingers102 retracted, but capable of alignment with the notches 43 and 53 ofthe shaping molds 40 and 50 upon extension.

The timer T6 also resets all the limit switches and timers so that theycan be actuated in the sequence recited above during a succeeding cycle.In addition, timer T-6 opens solenoid valves SV1 and SV-2 to permitheated gas to enter mold chambers 42 and 52 to raise the moldtemperatures to the desired temperature range. The rate of flow is againpreferably between 300 and 350 cubic feet per minute of the combustionproducts of natural gas per square foot of mold shaping surface. Thisrate suflices to raise the molds to the desired temperature range of 600to 750 degrees Fahrenheit without wasting excess combustion products.

It is understood that the present invention may be used in horizontalpressing apparatus comprising one mold of the type depicted by convexmold 40 in combination with an open ring type mold. Preheating aforaminous mold to the proper temperature range causes equal heatexchange along opposite major glass sheet surfaces even though one moldis continuous and the other of the open ring type.

Several experiments were performed to determine optimum parameters forquenching pressed glass sheets. In these experiments, apertures 67 werearranged in parallel rows /2 inch apart. The apertures in each row were/8 inch diameter spaced /2 inch apart center to center and the rows wereskewed at a 15 degree angle to the axis of relative movement between theglass sheet and the press bending molds.

The following parameters listed in Table I were verified as the minimumquenching times and minimum displacement at 60 cycles of reciprocationper minute to establish an acceptable temper in the glass previouslyheated to 1220 degrees Fahrenheit before being press bent and quenched(one in which the glass developed a surface compression stress of atleast 22,000 pounds per square inch).

Previous work on glass tempering had indicated that commercialsoda-lime-silica composition of sheet glass, plate glass and float glasshad insignificant differences from one another in parameters foridentical thicknesses, heating cycles, nozzle or apertureconfigurations, mold to mold separation during quenching, rate of coldair flow and displacement during relative oscillation between the bentglass and the apertured molds during quenching.

The form of the invention shown and described in this disclosurerepresents an illustrative preferred embodiment thereof. It isunderstood that various changes may be made without departing from thespirit of the invention as defined in the claimed subject matter whichfollows. For example, an operative apparatus may have only the lowermold 40 movable vertically instead of 10 moving both molds of theillustrative horizontal press bending apparatus.

What is claimed is:

1. A method of shaping and cooling a glass sheet disposed in a generallyhorizontal position at a desired location,

press shaping said sheet to a desired curvature at said location withopposing foraminous surfaces,

moving at least one of said foraminous surfaces to separate saidforaminous surfaces, said glass sheet remaining in contact with one ofsaid foraminous surfaces,

applying heated fluid through said foraminous surface in contact withsaid glass sheet at a pressure sufficient to separate said glass sheetfrom said foraminous sheet in contact therewith, and

applying chilling medium through each of said foraminous surfaces tosaid glass sheet at a pressure sufficient to support said glass sheetand until said glass sheet is no longer in a deformable state.

2. A method of shaping and cooling a glass sheet at a location in agenerally horizontal path through which said glass sheet is conveyedcomprising moving said sheet into said location,

press shaping said sheet to a desired curvature at said location withopposing foraminous surfaces,

moving at least one of said foraminous surfaces to separate saidforaminous surfaces, said glass sheet remaining in contact with one ofsaid foraminous surfaces,

applying heated air through said foraminous surface in contact with saidglass sheet at a pressure sufiicient to separate said glass sheet fromsaid foraminous surface in contact therewith, and

applying cool air through each of said foraminous surfaces to said glasssheet at a pressure suflicient to support said glass sheet and untilsaid glass sheet is no longer in a deformable state.

3. Apparatus for bending and cooling glass sheets, comprising a pressshaping mold and a light weight frame at a single station, a pair ofsets of fingers fixed to said frame for movement therewith, each fingerof one set being spaced from a finger of the other set by a distanceslightly greater than the glass sheet dimension along a line connectingsaid fingers, means supporting said frame relative to said mold, andmeans to impart a to-and-fromotion to said frame in a generallyhorizontal direction and along an axis parallel to said line connectingsaid fingers, whereby when a bent glass sheet is supported adjacent ashaping surface of said mold, said fingers alternately engage oppositeedges of said supported glass sheet to impart a generally horizontalto-and-fro motion to said supported glass sheet until said glass sheetis cooled and is no longer in a deformable state.

4. Apparatus as in claim 3, comprising a pair of press shaping moldmembers, each mold member having a plenum chamber and an outer,foraminous wall having a contour conforming to the shape desired for themaior surface of a glass sheet it opposes during press bending, meansfor introducing cold fluid into said chamber for exhaust through saidforamina at a rate sufficiently rapid to impart a temper to said glasssheet after the latter is shaped to its desired contour, and means toactuate said to-and-fro motion of said frame in synchronism with theintroduction of cold fluid into said chambers.

5. Apparatus as in claim 4, wherein said molds include one mold having aforaminous wall of concave contour and another mold having a foraminouswall of convex contour and means providing relative movement betweensaid contoured walls between a retracted position and a closed position.

6. Apparatus as in claim 5, further including control means forintroducing fluid into the chamber of said mold having a foraminous wallof convex contour only upon providing relative movement of said moldsfrom said closed position to help disengage said bent glass sheet fromsaid molds.

7. Apparatus as in claim 5, wherein said molds cornprise an upper moldand a lower mold disposed above and below one another and said frame issupported for movement on said upper mold and is provided with aclearance notch to receive each of said fingers.

8. Apparatus as in claim 7, wherein said lower mold is provided with aclearance notch aligned with each of said clearance notches provided onsaid upper mold.

9. Apparatus as in claim 8, further including a horizontal conveyorincluding stub rolls aligned with said clearance notches on said lowermold.

10. Apparatus as in claim 7, wherein said upper mold has a downwardlyfacing, concave, foraminous wall recessed upward from a horizontal planeand said lower mold has an upwardly facing, convex, foraminous wallprotruding upward from a horizontal plane.

'11. The method of claim 2 wherein said cool air applied to said glasssheet is applied at a rate and at a temperature suflicient to tempersaid glass sheet.

12. A method of shaping and cooling a glass sheet disposed in agenerally horizontal position at a single station,

press shaping said sheet to a desired curvature at said station withopposing foraminous surfaces,

moving at least one of said foraminous surfaces to separate saidforaminous surfaces, said glass sheet remaining in contact with one ofsaid foraminous surfaces,

applying fluid through said foraminous surface in contact with saidglass sheet at a pressure sufficient to separate said glass sheet fromsaid foraminous surface in contact therewith,

engaging opposite edges of said glass sheet and applying reciprocatingforces at said station in a generally horizontal direction to theopposing edges of said sheet at the points of engagement therewith, saidforces being suflicient to impart reciprocating movement to said glasssheet in opposite generally horizontal directions and until said glasssheet is no longer in a deformable state.

13. A method of shaping and cooling a glass sheet at a single station ina generally horizontal path through which said glass sheet is conveyedcomprising moving said sheet into said station,

press shaping said sheet to a desired curvature at said station withopposing foraminous surfaces,

moving at least one of said foraminous surfaces to separate saidforaminous surfaces, said glass sheet remaining in contact with one ofsaid foraminous surfaces,

applying fluid through said foraminous surface in contact with saidglass sheet at a pressure sufficient to separate said glass sheet fromsaid foraminous surface in contact therewith,

engaging opposite edges of said glass sheet and applying reciprocatingforces at said station in a generally horizontal direction to theopposing edges of said sheet at the point of engagement therewith, saidforces being sufiicient to impart reciprocating movement to said glasssheet in opposite generally horizontal directions and until said glasssheet is no longer in a deformable state.

14. A method of shaping and cooling a glass sheet at a single station ina generally horizontal path through which said glass sheet is conveyedcomprising moving said sheet into said station,

press shaping said sheet to a desired curvature at said station withopposing foraminous surfaces,

moving at least one of said foraminous surfaces to separate saidforaminous surfaces, said glass sheet remaining in contact with one ofsaid foraminous surfaces,

12 applying fluid through said foraminous surface in contact with saidglass sheet at a pressure sufiicient to separate said glass sheet fromsaid foraminous surface in contact therewith, applying chilling mediumthrough each of said foraminous surfaces to said glass sheet at apressure sufficient to support said glass sheet,

engaging opposite edges of said glass sheet while said sheet is sosupported, and

applying reciprocating forces at said station in a generally horizontaldirection to the opposing edges of said sheet at the points ofengagement therewith while said chilling medium is applied through eachof said foraminous surfaces to said glass sheet, said forces beingsufiicient to impart reciprocating movement to said glass sheet inopposite generally horizontal directions, said chilling medium and saidforces being applied to said glass sheet until said sheet is no longerin a deformable state.

15. The method of claim 14 wherein said chilling medium applied to saidglass sheet is applied at a rate and at a temperature suflicient totemper said glass sheet.

16. An apparatus for shaping and cooling a glass sheet as in claim 14further comprising a pair of press shaping mold members, each of saidmembers having opposing foraminous shaping surfaces and a plenum meansfor supplying a gas through the foramina of each of said foraminousmembers,

means for moving one of said mold members to separate the foraminoussurfaces of said mold members, means for supplying a heated gas to atleast one of said plenum chambers and means for supplying a cooled gasto each of said plenum chambers.

17. A method of shaping and cooling a glass sheet at a single station ina generally horizontal path through which said glass sheet is conveyedcomprising moving said sheet into said station,

press shaping said sheet to a desired curvature at said station withopposing foraminous surfaces,

moving at least one of said foraminous surfaces to separate saidforaminous surfaces,

applying chilling medium through each of said foraminous surfaces tosaid glass sheet at a pressure sufficient to support said glass sheet,engaging opposite edges of said glass sheet while said sheet is sosupported, and

applying reciprocating forces at said station in a generally horizontaldirection to the opposing edges of said sheet at the points ofengagement therewith while said chilling medium is applied through eachof said foraminous surfaces to said glass sheet, said forces beingsufficient to impart reciprocating movement to said glass sheet inopposite generally horizontal directions, said chilling medium and saidforces being applied to said glass sheet until said sheet is no longerin a deformable state.

References Cited UNITED STATES PATENTS 3,279,906 1/ 1966 Baker 65275X3,468,645 9/1969 McMaster et al 65--182X 3,485,612 12/1969 McMaster65182X 3,488,173 1/1970 McMaster 65-182X ARTHUR D. KELLOGG, PrimaryExaminer US. Cl. X.R.

